Daily Politics and Economics comment. Co-Author of How to Lose a Referendum – the Definitive Story of Why Britain Voted for Brexit [http://bit.ly/2ryynRG]. Economics and Politics teacher in London. 7 years' Independent experience after 4 years in the state sector. Prior to that a management consultant. All opinions here are my own

In an operation that has been ongoing for a week – the Islamic State of Iraq and Al-Shams (ISIS) seized control of the western half of Mosul, Iraq’s second largest city and a major political and economic centre in the northern Nineveh province. (Yes, Bible-fans, the Nineveh in the Jonah and the Whale story). Although Iraqi security forces outnumbered ISIS fighters by more than 15-to-one, they suffered a dramatic collapse of morale – partly, it is suggested, because they thought they were being asked to to fight fellow Iraqis. By Tuesday, ISIS had overrun the provincial council and governor’s offices, high security prisons, the Federal Police headquarters, television stations and the international airport. They now have a proper foothold in the West of Iraq, and the eyes of the world are on that area, because what happens now could reshape not only that area of the Middle East but also global politics as a whole.

If ISIS were to develop firm control of Iraq’s second city they would have replicated their success in seizing an administrative and economic capital in Syria’s Raqqa province. They could therefore continue to consolidate a caliphate covering a population of over a million people, a greater success than anything they achieved in Syria – which was where they started out (but have had less success due to President Assad’s, shall we say, rather aggressive response to their actions). For this reason we can expect hard fighting to follow as the Iraqi government uses every resource at its disposal – military forces, new local militias, air power, Iranian-backed Shia volunteers from southern militias, the Kurdish Peshmerga plus US intelligence and logistical support.

The battle for Mosul is shaping up to be a critical test of the political and military vitality of the Iraqi state. Interestingly, there have been reports of former Baath party members joining forces with the Jihadists – and raising posters of Saddam Hussein once the Iraqi army had been driven out – particularly in Tikrit, his hometown. The Prime Minister – Nouri Al-Maliki – held a vote to grant himself emergency powers to combat ISIS but found that only 128 out of 325 fighters turned up for the vote – meaning he couldn’t get a quorum to do so. This is how fragmented Iraqi politics is.

The success of ISIS can only make the turmoil in the Middle East worse. ISIS is an ultra extremist Sunni Muslim group. Its success will deepen the sectarian conflict between Sunnis and Shias that is already the most dangerous fault line in the Middle East. Iran, which is a majority Shia Muslim country, shares a border with Iraq. It has a direct line to Iraq’s Shia Muslim Prime Minister, Nouri Maliki, and close links with some Iraqi Shia militias. The Iranians could direct their proxies, and even their own special forces units, at ISIS. That might end up further inflaming the anger of Iraqi Sunnis, who have already helped the advance of ISIS through Iraq. US air strikes, if they happen, might do the same thing. Once again in the Middle East, the Americans have limited options. Its invasion and occupation of Iraq in 2003 helped create and strengthen jihadist groups.

It has not escaped the notice of observers of that area of the world that ISIS could well be using Western supplied weapons that they were offered as supposed “rebels” against Assad in Syria- which again supports the caution people have been urging about finding out exactly who we are actually helping.

The point is – what you are seeing is a game of chess – with every potential move fraught with danger. The problem is – it’s not a game, it’s real.